A bionic double-manganese core-shell structure catalyst and a preparation method and application thereof

Abstract

This invention discloses a biomimetic dual-manganese core-shell structure catalyst, its preparation method, and its application, belonging to the field of indoor air purification catalyst preparation technology. The method involves converting a MnCO3 precursor into porous Mn2O3 nanorods through programmed temperature calcination in an air atmosphere, serving as the core material. Microwave-assisted redox etching is then performed on the core material to grow vertically oriented MnO2 nanosheet shells in situ on its surface, yielding a core-shell structure intermediate. This intermediate is then acid-activated and post-treated to obtain a biomimetic dual-manganese core-shell structure Mn2O3@MnO2. This catalyst features a rationally designed structure, a controllable preparation method, and exhibits high activity, high stability, and good environmental adaptability, making it promising for applications in indoor air purification and other fields.

Description

Technical Field

[0001] This invention belongs to the field of indoor air purification catalyst preparation technology, specifically relating to a biomimetic dual manganese core-shell structure catalyst, its preparation method, and its application. Background Technology

[0002] With the increase in indoor decoration activities, plywood, MDF, particleboard, and other engineered wood products are widely used in building decoration, furniture manufacturing, and interior decoration. The production processes of these products generally employ aldehyde-containing adhesives such as urea-formaldehyde resin and phenol-formaldehyde resin. Because these adhesives continuously decompose and release free formaldehyde during curing and subsequent use, with a volatilization period of 3 to 15 years, formaldehyde has become one of the most significant volatile organic pollutants in indoor air. According to the classification of the International Agency for Research on Cancer (IARC) of the World Health Organization, formaldehyde has been officially classified as a Group 1 carcinogen for humans. Long-term exposure to formaldehyde pollution not only significantly increases the risk of malignant diseases such as nasopharyngeal carcinoma and leukemia, but also causes irreversible damage to the human respiratory, nervous, and immune systems. Given the prevalence and long-term nature of formaldehyde pollution and its serious threat to public health, research on efficient and sustainable indoor formaldehyde purification technologies has significant practical implications and public health value.

[0003] Currently, indoor formaldehyde treatment methods mainly include physical adsorption, chemical capture, biodegradation, and catalytic oxidation. Among them, catalytic oxidation technology is considered one of the most promising treatment methods because it can directly convert formaldehyde into harmless CO2 and H2O, exhibiting significant advantages such as high thoroughness and low risk of secondary pollution.

[0004] In catalytic oxidation technology, traditional noble metal catalysts (such as platinum and palladium) exhibit excellent catalytic activity at low temperatures, but their high cost, sensitivity to moisture, and long-term stability issues limit their large-scale application in practical indoor environments. Therefore, researchers have gradually turned their attention to transition metal oxide systems, among which manganese-based oxides, due to their variable valence state (Mn... 3+ / Mn 4+ It has attracted much attention due to its excellent oxygen transport capacity and low cost.

[0005] However, the catalytic performance of manganese-based oxides in the room temperature to low temperature range still faces several key challenges: on the one hand, their low-temperature activity is insufficient, making it difficult to meet the high-efficiency purification requirements under normal indoor temperature conditions; on the other hand, in high humidity environments, active sites are easily occupied by water molecules or the structure collapses, resulting in poor moisture resistance; in addition, due to the tendency of particles to agglomerate, the accessibility of active sites is limited, which further restricts their catalytic efficiency.

[0006] In conclusion, developing manganese-based catalysts that combine high activity, high stability, and good moisture resistance has become an important direction for research in indoor formaldehyde purification technology. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem that existing manganese-based catalysts cannot simultaneously possess high activity, high stability, and good moisture resistance. This invention proposes a biomimetic dual manganese core-shell structure catalyst, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a biomimetic dual-manganese core-shell structure catalyst, comprising the following steps: MnCO3 precursor was converted into porous Mn2O3 nanorods by programmed calcination in air atmosphere, which were used as core materials. Microwave-assisted redox etching was performed on the nuclear material to grow vertically oriented MnO2 nanosheet shells in situ on the surface of the nuclear material, thus obtaining a core-shell structure intermediate product. The core-shell structure intermediate was activated by acid and post-treated to obtain a biomimetic dual manganese core-shell structure Mn2O3@MnO2.

[0009] Furthermore, the preparation method of the MnCO3 precursor includes the following steps: Manganese sulfate monohydrate is dissolved in a water / ethylene glycol mixed solvent to form solution A; Dissolve ammonium bicarbonate in water to form solution B; Solution B was added dropwise to solution A with stirring at room temperature, and the precipitate was obtained after aging following the reaction. The precipitate was centrifuged, washed, and dried to obtain the MnCO3 precursor.

[0010] Furthermore, when preparing the MnCO3 precursor, the amounts of each raw material are as follows: MnSO4·H2O is 1.0–3.0 g, deionized water in the water / ethylene glycol mixed solvent is 20–60 mL, ethylene glycol is 5–15 mL, ammonium bicarbonate is 1.0–4.0 g, and deionized water in solution B is 30–50 mL.

[0011] Furthermore, when preparing the MnCO3 precursor, the dropwise addition time of solution B is 20–60 min; after the dropwise addition is completed, stirring is continued for 2–6 h, and the aging time is 10–24 h; the centrifugation speed is 6000–10000 rpm, and the centrifugation time is 10–20 min; washing is performed by washing with deionized water and ethanol 3–6 times respectively; the drying temperature is 60–80℃, and the drying time is 12–20 h.

[0012] Furthermore, the method for obtaining porous Mn2O3 nanorods is as follows: MnCO3 precursor is placed in a corundum boat, placed in a tube furnace, and calcined under programmed temperature rise in air atmosphere to obtain porous Mn2O3 nanorods. The calcination conditions are as follows: heating rate of 1-5℃ / min, calcination temperature of 400-600℃, and constant temperature time of 4-6h; after calcination, the food is allowed to cool naturally to room temperature.

[0013] Furthermore, the method for constructing the MnO2 nanosheet shell includes the following steps: Porous Mn2O3 nanorods were dispersed in water to form a suspension. Potassium permanganate was added to the suspension, and the mixture was transferred to a polytetrafluoroethylene-lined microwave digestion vessel. The mixture was then subjected to microwave reaction in a microwave synthesis system, utilizing the low-valent manganese on the core surface and MnO4. - Driven by redox reactions and lattice mismatch stress, MnO2 nanosheets are specifically induced to grow vertically on the Mn2O3 surface, forming core-shell structured intermediates that resemble foxtail grass.

[0014] Furthermore, the microwave reaction conditions are as follows: Mn2O3 dosage is 1.0 g, dispersion water volume is 20–80 mL, ultrasonic dispersion time is 5–30 min; KMnO4 dosage is 0.45–7.3 g; microwave reaction temperature is 120–160 °C, reaction time is 10–60 min, and power is 200–600 W. In core-shell structured intermediates, the mass ratio of Mn2O3 / MnO2 ranges from (2~8):(8~2).

[0015] Furthermore, acid activation and post-treatment include the following steps: After centrifugation and washing, the core-shell intermediate product was redispersed in 0.1–0.5 M nitric acid solution and stirred at room temperature for 2–4 h. It was then washed with deionized water until the supernatant was neutral, and finally freeze-dried for 12–24 h at a temperature of -30 to -10 °C.

[0016] Secondly, the present invention provides a biomimetic dual-manganese core-shell structure catalyst, which is prepared using the above-described method for preparing the biomimetic dual-manganese core-shell structure catalyst.

[0017] Thirdly, this invention provides the application of a biomimetic dual manganese core-shell structure catalyst in the catalytic oxidation of formaldehyde.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: This invention proposes a method for preparing a biomimetic dual-manganese core-shell structure catalyst. By constructing a biomimetic core-shell structure of "porous Mn2O3 core / vertical MnO2 nanosheet shell," it achieves highly efficient low-temperature catalytic oxidation of indoor formaldehyde. Specifically, the advantages of this structure are reflected in: (1) Interfacial synergistic effect: A tight heterogeneous interface is formed between the Mn2O3 core and the MnO2 shell, constructing Mn 3+ / Mn 4+ Reversible redox coupling pairs effectively promote interfacial electron transfer and the continuous generation of reactive oxygen species; (2) Improved mass transfer and exposure efficiency: The porous core provides open diffusion channels and high specific surface area, and the vertically grown MnO2 nanosheet shell further increases the exposure of active sites on the outer surface, significantly improving gas-solid contact efficiency and reactant mass transfer capacity. (3) Surface defect regulation: By removing intercalated ions through acid activation treatment, a rich surface defect structure is induced, which is conducive to the adsorption and activation of O2 and the migration and diffusion of lattice oxygen, thereby maintaining a high reaction rate in the range of room temperature to low temperature. (4) Enhanced moisture resistance: The “foxtail grass”-like hierarchical structure can maintain high accessibility of active sites in the presence of water vapor, effectively inhibiting deactivation caused by competitive adsorption of water molecules, and showing excellent resistance to water vapor deactivation and long-term operational stability.

[0019] In summary, the catalyst of this invention has a reasonable structural design and a controllable preparation method, and possesses high activity, high stability, and good environmental adaptability, making it a promising candidate for applications in fields such as indoor air purification. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] The present invention will now be described in further detail: A method for preparing a biomimetic dual-manganese core-shell structure Mn2O3@MnO2 catalyst includes the following steps: First, a MnCO3 precursor was prepared and calcined to obtain a porous Mn2O3 nanorod core; then, a vertically oriented MnO2 nanosheet shell was grown in situ on the core surface by microwave-assisted redox etching; finally, the target catalyst was obtained by dilute acid activation and freeze-drying.

[0022] The preparation method of the above-mentioned MnCO3 precursor is as follows: Manganese sulfate monohydrate was dissolved in a mixed solvent of deionized water and ethylene glycol, and the solution was magnetically stirred to form solution A. Ethylene glycol served as a morphology directing agent to adjust the solution viscosity and nucleation rate. Ammonium bicarbonate was dissolved in deionized water to form solution B. Solution B was added dropwise to solution A under stirring at room temperature. The mixture was stirred continuously and then allowed to stand for aging. The resulting white precipitate was collected by centrifugation, washed with deionized water and ethanol, and finally dried overnight in an oven to obtain rod-shaped MnCO3 precursor.

[0023] When preparing the MnCO3 precursor, the amounts of each raw material are as follows: MnSO4·H2O is 1.0–3.0 g, ammonium bicarbonate is 1.0–4.0 g; in the mixed solvent, deionized water is 20–60 mL, ethylene glycol is 5–15 mL; and in solution B, deionized water is 30–50 mL.

[0024] When preparing the MnCO3 precursor, the dropwise addition time of solution B is 20–60 min; after the dropwise addition is completed, stirring is continued for 2–6 h, and the aging time is 10–24 h; the centrifugation speed is 6000–10000 rpm, and the centrifugation time is 10–20 min; washing is performed by washing with deionized water and ethanol 3–6 times respectively; the drying temperature is 60–80℃, and the drying time is 12–20 h.

[0025] The preparation method of the above porous Mn2O3 nanorods is as follows: The MnCO3 precursor was placed in a tube furnace; it was calcined under a programmed temperature rise in air and held at that temperature; after calcination, it was naturally cooled to room temperature to obtain porous Mn2O3 nanorods.

[0026] The calcination conditions are as follows: heating rate of 1-5℃ / min, calcination temperature of 400-600℃, and constant temperature time of 4-6h; after calcination, the food is allowed to cool naturally to room temperature.

[0027] The above-mentioned method for constructing a foxtail grass-like core-shell structure is as follows: A microwave-assisted surface redox etching strategy was used to ultrasonically disperse porous Mn2O3 nanorods in deionized water to form a uniform suspension, followed by the addition of KMnO4. The mixture was then transferred to a polytetrafluoroethylene-lined microwave digestion vessel and reacted in a microwave synthesis system.

[0028] The microwave reaction conditions were as follows: Mn₂O₃ dosage was 1.0 g, dispersion water volume was 20–80 mL, and ultrasonic dispersion time was 5–30 min; KMnO₄ dosage was 0.45–7.3 g; microwave reaction temperature was 120–160℃, reaction time was 10–60 min, and power was 200–600 W. The mass ratio of Mn₂O₃ / MnO₂ ranged from (2:8) to (8:2).

[0029] The above acid activation and post-treatment steps are as follows: The product obtained from the microwave reaction was collected by centrifugation and washed with deionized water; this was to remove K intercalated from the layers. + Ions generate abundant surface defect sites. The moist precipitate is redispersed in HNO3 solution and stirred at room temperature. Finally, the product is washed with deionized water until the supernatant is neutral and then freeze-dried to obtain a biomimetic dual manganese core-shell structure Mn2O3@MnO2 catalyst.

[0030] Acid activation and post-treatment were performed as follows: the product obtained from the microwave reaction was centrifuged, washed, and redispersed in 0.1–0.5 M nitric acid solution and stirred at room temperature for 2–4 h; then washed with deionized water until the supernatant was neutral, and finally freeze-dried for 12–24 h (-30 to -10 °C) to inhibit the aggregation of nanosheet shells.

[0031] This invention also provides the application of a biomimetic dual-manganese core-shell structure catalyst in the catalytic oxidation of formaldehyde at room temperature.

[0032] This invention relates to a manganese-based catalyst for formaldehyde purification, its preparation method, and its application. The catalyst is a biomimetic dual-manganese core-shell structure Mn2O3@MnO2, with a porous Mn2O3 nanorod core and an outer shell of in-situ grown MnO2 nanosheets, exhibiting a layered morphology resembling "foxtail grass." Preparation involves obtaining a nanorod MnCO3 precursor via an ethylene glycol-controlled precipitation reaction, followed by slow calcination in air to release CO2, create pores, and convert it to Mn2O3. Under microwave irradiation, permanganate is introduced to induce surface redox etching-reconstruction, allowing MnO2 nanosheets to grow vertically and oriented on the core surface to construct the shell. Further, mild activation with dilute nitric acid removes intercalated ions and introduces defect sites. After washing and freeze-drying, the biomimetic dual-manganese core-shell structure Mn2O3@MnO2 is obtained. This catalyst combines porous mass transfer channels, abundant interfacial sites, and reversible MnO2 formation. 3+ / Mn 4+ It is a redox center that exhibits high activity and stability in the oxidation of formaldehyde in the range of room temperature to low temperature, making it suitable for indoor air purification and other applications.

[0033] The present invention will be further described in detail below with reference to the embodiments: Example 1 This embodiment provides a biomimetic dual-manganese core-shell structured Mn2O3@MnO2 catalyst, the preparation method of which includes the following steps: (1) Weigh 2.0 g of manganese sulfate monohydrate (MnSO4·H2O) and place it in a beaker. Dissolve it in a mixed solvent consisting of 40 mL of deionized water and 10 mL of ethylene glycol. Stir magnetically until completely dissolved to form solution A. Dissolve 2.5 g of ammonium bicarbonate in 40 mL of deionized water to form solution B. Under stirring at room temperature (600 rpm), add solution B dropwise to solution A over a period of 40 min. Continue stirring for 4 h and then let it stand for 15 h. Collect the precipitate by centrifugation at 8000 rpm for 15 min. Wash it 5 times each with deionized water and ethanol. Finally, dry it in an oven at 70 °C for 15 h to obtain the MnCO3 precursor.

[0034] (2) Place the MnCO3 precursor into a tube furnace; heat it to 500℃ at 2℃ / min in air atmosphere and hold it for 5h, then cool it naturally to room temperature to obtain porous Mn2O3 nanorods.

[0035] (3) Disperse 1gMn2O3 in 50mL of deionized water and sonicate for 20min to form a uniform suspension. Add 0.45gKMnO4 and transfer to a 100mL polytetrafluoroethylene-lined container. React at 140℃ for 30min (300W) in a microwave synthesis system to obtain a biomimetic "foxtail grass" core-shell structure intermediate.

[0036] (4) The obtained product was centrifuged and washed, then redispersed in 50 mL of 0.3 M nitric acid solution and stirred at room temperature for 3 h; then washed with deionized water until the supernatant was neutral, and freeze-dried for 15 h (-20 °C) to obtain a biomimetic dual manganese core-shell structure Mn2O3@MnO2 catalyst, denoted as C1. The mass ratio of Mn2O3 / MnO2 was 8:2.

[0037] Example 2 Using the same method as in Example 1, except that the amount of KMnO4 added in step (3) was changed to 1.8g, the resulting sample was denoted as C2, and the mass ratio of Mn2O3 / MnO2 was 5:5.

[0038] Example 3 Using the same method as in Example 1, except that the amount of KMnO4 added in step (3) was changed to 7.3g, the resulting sample was denoted as C3, and the mass ratio of Mn2O3 / MnO2 was 2:8.

[0039] Comparative Example 1 (1) Weigh 2.0 g of manganese sulfate monohydrate (MnSO4·H2O) and place it in a beaker. Dissolve it in a mixed solvent consisting of 40 mL of deionized water and 10 mL of ethylene glycol. Stir magnetically until completely dissolved to form solution A. Dissolve 2.5 g of ammonium bicarbonate in 40 mL of deionized water to form solution B. Under stirring at room temperature (600 rpm), add solution B dropwise to solution A over a period of 40 min. Continue stirring for 4 h and then let it stand for 15 h. Collect the precipitate by centrifugation at 8000 rpm for 15 min. Wash it 5 times each with deionized water and ethanol. Finally, dry it in an oven at 70 °C for 15 h to obtain the MnCO3 precursor.

[0040] (2) Place the MnCO3 precursor into a tube furnace; heat it to 500℃ at 2℃ / min in an air atmosphere and hold it for 5h, then cool it naturally to room temperature to obtain porous Mn2O3 nanorods, denoted as D1.

[0041] Comparative Example 2 (1) Weigh 0.45g KMnO4 and dissolve it in 50mL of deionized water. Then transfer it to a 100mL polytetrafluoroethylene-lined container and react it in a microwave synthesis system at 140℃ for 30min (300W) to obtain MnO2.

[0042] (2) After centrifugation and washing, the obtained product was redispersed in 50 mL of 0.3 M nitric acid solution and stirred at room temperature for 3 h. Then it was washed with deionized water until the supernatant was neutral and freeze-dried for 15 h (-20 °C) to obtain the MnO2 catalyst, denoted as D2.

[0043] The application test is as follows: The catalyst was evaluated in a micro fixed-bed reactor. 50 mg of catalyst (40–60 mesh) was weighed and packed into a U-shaped reaction tube (id = 6 mm). Formaldehyde was generated by passing air (21 vol.% O2 / N2) at a flow rate of 50 mL / min through the U-shaped tube containing paraformaldehyde. The reaction conditions were: 20–300 ppm HCHO, 10–80% RH (relative humidity), and a mass hourly space velocity (WHSV) of 60,000 mL g. cat -1 h -1 The analysis was performed using gas chromatography equipped with a flame ionization detector (FID), a thermal conductivity detector (TCD), and a Ni conversion furnace. Formaldehyde conversion rate ( X 甲醛 The calculation method is as shown in formula (1).

[0044]

[0045] Table 1 lists the catalyst preparation conditions and catalyst performance evaluation of the examples. Reaction conditions: 200 ppm HCHO, 50% RH (relative humidity), mass hourly space velocity (HHSV) of 60000 mL g. cat -1 h -1 .

[0046] Table 1 Performance of different catalysts in catalytic oxidation of formaldehyde

[0047] Table 2 lists the effect of formaldehyde concentration on the performance of C2 catalytic oxidation of formaldehyde. Reaction conditions: 20~300ppm HCHO, 50%RH (relative humidity), mass hourly space velocity (WHSV) of 60000 mL g. cat -1 h -1 .

[0048] Table 2 Effect of formaldehyde concentration on the performance of C2 catalytic oxidation of formaldehyde

[0049] Table 3 lists the effect of humidity on the performance of C2 catalytic oxidation of formaldehyde. Reaction conditions: 200 ppm HCHO, 10~80% RH (relative humidity), mass hourly space velocity (HHSV) of 60000 mL g. cat -1 h -1 .

[0050] Table 3 Effect of relative humidity on the performance of C2 catalytic oxidation of formaldehyde

[0051] Table 4 lists the effect of reaction time on the performance of C2 catalytic oxidation of formaldehyde. Reaction conditions: 200 ppm HCHO, 50% RH (relative humidity), and a mass hourly space velocity (WHSV) of 60,000 mL g. cat -1 h -1 .

[0052] Table 4 Effect of reaction time on the performance of C2 catalytic oxidation of formaldehyde

[0053] As shown in Table 1, at 30℃, the formaldehyde conversion rates of D1 and D2 were 35.5% and 45.3%, respectively. The catalyst performance was significantly improved after constructing the biomimetic dual-manganese Mn2O3 / MnO2 core-shell structure. In particular, the formaldehyde conversion rate of C2 reached 97.9% at 20℃, and formaldehyde was completely converted to CO2 and H2O at 30℃. This indicates a significant synergistic catalytic effect between Mn2O3 and MnO2. This synergistic effect is mainly reflected in the following aspects: First, the heterogeneous interface between Mn2O3 and MnO2 promotes the conversion of Mn2O3 into CO2 and H2O. 3+ Mn 4+ The reversible redox cycle accelerates electron transfer and the generation of reactive oxygen species. Secondly, the vertical growth of MnO2 nanosheets significantly enhances the exposure of active sites on the outer surface and the gas-solid contact efficiency. Furthermore, the porous Mn2O3 core provides open mass transfer channels and high adsorption capacity, making it easier for formaldehyde molecules to be captured by defect-rich sites and undergo deep oxidation at the interface. In summary, the biomimetic dual-manganese core-shell structure catalyst combines high low-temperature oxidation activity with good stability, demonstrating promising application prospects.

[0054] According to the data in Table 2, catalyst C2 exhibits excellent catalytic oxidation performance within a formaldehyde concentration range of 20–300 ppm. When the formaldehyde concentration is below 300 ppm, the conversion rate of formaldehyde by C2 remains stable at over 95.0% at 20°C, indicating its suitability for formaldehyde purification applications across a wide concentration range.

[0055] Table 3 further investigates the effect of relative humidity (10%–80%) on the catalytic activity of the C2 catalyst. The results show that, under different humidity conditions at 20℃, the conversion rate of formaldehyde by C2 remains above 90%, demonstrating good moisture resistance and humidity adaptability.

[0056] Table 4 summarizes the stability performance of catalyst C2 during the continuous reaction process. At 20℃ for 50 hours, the conversion rate of formaldehyde by C2 remained stable at approximately 95.0%; when the reaction temperature was increased to 30℃, the conversion rate remained at 100% for 50 hours, fully demonstrating the excellent reaction stability and long-term use potential of this catalyst.

[0057] Many embodiments and applications beyond the examples provided will be apparent to those skilled in the art upon reading the foregoing description. Therefore, the scope of this teaching should not be determined by reference to the foregoing description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

[0058] The above content provides a further detailed description of the present invention. It should not be construed that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the defined protection scope of the present invention.

Claims

1. A method for preparing a biomimetic dual-manganese core-shell structure catalyst, characterized in that, Includes the following steps: MnCO3 precursor was converted into porous Mn2O3 nanorods by programmed calcination in air atmosphere, which were used as core materials. The core material was subjected to microwave-assisted redox etching, and vertically oriented MnO2 nanosheet shells were grown in situ on the surface of the core material to obtain a core-shell structure intermediate product. The core-shell structure intermediate was activated by acid and post-treated to obtain a biomimetic dual manganese core-shell structure Mn2O3@MnO2.

2. The method for preparing a biomimetic dual-manganese core-shell structure catalyst according to claim 1, characterized in that, The method for preparing the MnCO3 precursor includes the following steps: Manganese sulfate monohydrate is dissolved in a water / ethylene glycol mixed solvent to form solution A; Dissolve ammonium bicarbonate in water to form solution B; Solution B was added dropwise to solution A under stirring at room temperature, and the precipitate was obtained after aging following the reaction. The precipitate was centrifuged, washed, and dried to obtain the MnCO3 precursor.

3. The method for preparing a biomimetic dual-manganese core-shell structure catalyst according to claim 2, characterized in that, When preparing the MnCO3 precursor, the amounts of each raw material are as follows: MnSO4·H2O is 1.0–3.0 g, deionized water in the water / ethylene glycol mixed solvent is 20–60 mL, ethylene glycol is 5–15 mL, ammonium bicarbonate is 1.0–4.0 g, and deionized water in solution B is 30–50 mL.

4. The method for preparing a biomimetic dual-manganese core-shell structure catalyst according to claim 2, characterized in that, When preparing the MnCO3 precursor, the solution B is added dropwise over a period of 20–60 min; after addition, stirring is continued for 2–6 h, and aging is carried out for 10–24 h; the centrifugation speed is 6000–10000 rpm, and the centrifugation time is 10–20 min; washing is performed by washing with deionized water and ethanol 3–6 times respectively; the drying temperature is 60–80 °C, and the drying time is 12–20 h.

5. The method for preparing a biomimetic dual-manganese core-shell structure catalyst according to claim 1, characterized in that, The porous Mn2O3 nanorods are obtained by placing the MnCO3 precursor in a corundum boat, placing it in a tube furnace, and calcining it under a programmed temperature rise in an air atmosphere to obtain porous Mn2O3 nanorods. The calcination conditions are as follows: heating rate of 1-5℃ / min, calcination temperature of 400-600℃, and constant temperature time of 4-6h; after calcination, the food is allowed to cool naturally to room temperature.

6. The method for preparing a biomimetic dual-manganese core-shell structure catalyst according to claim 1, characterized in that, The method for constructing the MnO2 nanosheet shell includes the following steps: Porous Mn2O3 nanorods were dispersed in water to form a suspension; potassium permanganate was added to the suspension, and the mixture was transferred to a polytetrafluoroethylene-lined microwave digestion vessel for microwave synthesis. The reaction was carried out in a microwave synthesis system, utilizing the low-valent manganese on the core surface and MnO4... - The redox reaction and lattice mismatch stress drive the vertical growth of MnO2 nanosheets on the Mn2O3 surface, forming a core-shell structure intermediate product that is similar to foxtail grass.

7. The biomimetic dual-manganese core-shell structure catalyst according to claim 6, characterized in that, The microwave reaction conditions are as follows: Mn2O3 dosage is 1.0g, dispersion water volume is 20-80mL, ultrasonic dispersion time is 5-30min; KMnO4 dosage is 0.45-7.3g; microwave reaction temperature is 120-160℃, reaction time is 10-60min, and power is 200-600W. In the core-shell structured intermediate product, the mass ratio of Mn2O3 / MnO2 ranges from (2~8):(8~2).

8. The biomimetic dual-manganese core-shell structure catalyst according to claim 6, characterized in that, The acid activation and post-treatment include the following steps: The core-shell structure intermediate was centrifuged and washed, then redispersed in 0.1–0.5 M nitric acid solution and stirred at room temperature for 2–4 h. It was then washed with deionized water until the supernatant was neutral, and finally freeze-dried for 12–24 h at a temperature of -30 to -10 °C.

9. A biomimetic dual-manganese core-shell structure catalyst, characterized in that, It was prepared using the method for preparing a biomimetic dual manganese core-shell structure catalyst as described in any one of claims 1-8.

10. The application of the biomimetic dual manganese core-shell structure catalyst of claim 9 in the catalytic oxidation of formaldehyde.

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